An ion is a specie that have no unpaired electron and is charged, either positively or negatively i.e. may be a cation or an anion. It is formed due to heterolysis of a molecule e.g HCl----> H+ + Cl-
A radical is a neutral specie having atleast one unpaired electron and is formed due to homolysis of a molecule e.g
H-H -------> H* + H*
The * shows an unpaired electron. Similarly CH3* is a radical.

THERE NO DIFFERENCE BETWEEN PROCEDURE,BOTH ARE SAME.WE GENERALLY TERM IT AS SULPHATED ASH TEST/ROI.IN INDIAN PHARMACOEPIA,CALLED IT AS ROI AND IN USP,CALLED IT AS SULPHATED ASH TESH.BOTH ARE USED FOR THE DETERMINATION OF CONTENT OF INORGANIC MATTER IN AN ORGANIC SUBSTANCE.